/*
 * Copyright (c) 2010, 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package biz.ganttproject.lib.fx.treetable;

import com.sun.javafx.util.Utils;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.scene.control.IndexedCell;
import javafx.scene.control.ScrollBar;

/**
 * This custom ScrollBar is used to map the increment & decrement features
 * to pixel based scrolling rather than thumb/track based scrolling, if the
 * "virtual" attribute is true.
 */
public class VirtualScrollBar extends ScrollBar {

  /**************************************************************************
   *
   * Private fields
   *
   **************************************************************************/

  private final VirtualFlow flow;

  private boolean adjusting;



  /**************************************************************************
   *
   * Constructors
   *
   **************************************************************************/

  /**
   * Creates a new VirtualScrollBar, for use by the VirtualFlow control.
   */
  public VirtualScrollBar(final VirtualFlow flow) {
    this.flow = flow;

    super.valueProperty().addListener(valueModel -> {
      if (isVirtual()/* && oldValue != newValue*/) {
        if (adjusting) {
          // no-op
        } else {
          flow.setPosition(getValue());
        }
      }
    });
  }



  /**************************************************************************
   *
   * Properties
   *
   **************************************************************************/

  // --- virtual
  private BooleanProperty virtual = new SimpleBooleanProperty(this, "virtual");
  public final void setVirtual(boolean value) {
    virtual.set(value);
  }

  public final boolean isVirtual() {
    return virtual.get();
  }

  public final BooleanProperty virtualProperty() {
    return virtual;
  }


  /**************************************************************************
   *
   * Public API
   *
   **************************************************************************/

  /** {@inheritDoc} */
  @Override public void decrement() {
    if (isVirtual()) {
      flow.scrollPixels(-10);
    } else {
      super.decrement();
    }
  }

  /** {@inheritDoc} */
  @Override public void increment() {
    if (isVirtual()) {
      flow.scrollPixels(10);
    } else {
      super.increment();
    }
  }

  // this method is called when the user clicks in the scrollbar track, so
  // we special-case it to allow for page-up and page-down clicking to work
  // as expected.
  /** {@inheritDoc} */
  @Override public void adjustValue(double pos) {
    if (isVirtual()) {
      adjusting = true;
      double oldValue = flow.getPosition();

      double newValue = ((getMax() - getMin()) * Utils.clamp(0, pos, 1))+getMin();
      if (newValue < oldValue) {
        IndexedCell cell = flow.getFirstVisibleCell();
        if (cell == null) return;
        flow.scrollToBottom(cell);
      } else if (newValue > oldValue) {
        IndexedCell cell = flow.getLastVisibleCell();
        if (cell == null) return;
        flow.scrollToTop(cell);
      }

      adjusting = false;
    } else {
      super.adjustValue(pos);
    }
  }
}
